Keratin fibers, particularly human hair fibers, may be damaged over time. Damages may be caused by environmental factors, including air pollution, sun exposure, water pool, and/or rain. Damages may also be caused by applying to the fibers grooming (cosmetic), chemical and/or mechanical treatments. When hair fibers are damaged, the hair fibers may have undesirable conditions of, for example, “fly-away hair”, “split end”, and/or color fade.
Assessing the degree of damages caused to hair is of interest in order to understand the impact of various environmental factors as well as the impact of the cosmetic (grooming), chemical and mechanical treatments onto keratin fibers. Such assessment is also of interest in order to demonstrate the efficacy of treatments used for preventing and/or repairing hair damages. Several attempts for assessing hair damages, using different analytical methods, have already been reported. Such attempts include, for example, an assessment using hair volume measurement, and an assessment using hair color measurement. However, such assessments were not enough sensitive to show some differences, for example, efficacy difference among different conditioner products.
There is a need therefore for providing a method for assessing damages of keratin fibers, particularly, human hair fibers. Particularly, there is a need for providing a method for assessing damages of treated keratin fibers using cosmetic, chemical and/or mechanical treatments. In addition, there is also a need for providing a method for assessing and comparing damages of different keratin fibers, e.g. untreated fibers versus treated fibers or fibers treated with different treatments. As far as cosmetic compositions—particularly conditioning compositions—are concerned, there is a need for providing a method for assessing the efficacy of such compositions for preventing and/or repairing damages of hair fibers. There is also a need for providing a method for comparing the efficacy of two or more cosmetic compositions, particularly conditioning compositions, for preventing and/or treating damages of hair fibers. Finally, there is a need for providing a method for supporting advertising claims about the efficacy of a composition—or about the superiority of this composition versus a comparative composition—for preventing and/or repairing damages of hair fibers.